Osteoblastic differentiation of bone marrow mesenchymal stromal cells in Bruck Syndrome.

BACKGROUND: Osteogenesis Imperfecta (OI) (OMIM %259450) is a heterogeneous group of inherited disorders characterized by increased bone fragility, with clinical severity ranging from mild to lethal. The majority of OI cases are caused by mutations in COL1A1 or COL1A2. Bruck Syndrome (BS) is a further recessively-inherited OI-like phenotype in which bone fragility is associated with the unusual finding of pterygia and contractures of the large joints. Notably, several studies have failed to show any abnormalities in the biosynthesis of collagen 1 in BS patientes. Evidence was obtained for a specific defect of the procollagen telopeptide lysine hydroxylation in BS, whereas mutations in the gene PLOD2 have been identified. Recently, several studies described FKBP10 mutations in OI-like and BS patients, suggesting that FKBP10 is a bonafide BS locus. METHODS: We analyzed the coding region and intron/exon boundaries of COL1A1, COL1A2, PLOD2 and FKBP10 genes by sequence analysis using an ABI PRISM 3130 automated sequencer and Big Dye Terminator Sequencing protocol. Mononuclear cells obtained from the bone marrow of BS, OI patients and healthy donors were cultured and osteogenic differentiation was induced. The gene expression of osteoblast specific markers were also evaluated during the osteoblastic differentiation of mesenchymal stem cell (MSC) by qRT-PCR using an ABI7500 Sequence Detection System. RESULTS: No mutations in COL1A1, COL1A2 or PLOD2 were found in BS patient. We found a homozygous 1-base-pair duplication (c.831dupC) that is predicted to produce a translational frameshift mutation and a premature protein truncation 17 aminoacids downstream (p.Gly278ArgfsX95). The gene expression of osteoblast specific markers BGLAP, COL1A1, MSX2, SPARC and VDR was evaluated by Real Time RT-PCR during differentiation into osteoblasts and results showed similar patterns of osteoblast markers expression in BS and healthy controls. On the other hand, when compared with OI patients, the expression pattern of these genes was found to be different. CONCLUSIONS: Our work suggests that the gene expression profiles observed during mesenchymal stromal cell differentiation into osteoblast are distinct in BS patients as compared to OI patients. The present study shows for the first time that genes involved in osteogenesis are differentially expressed in BS and OI patients.

Impact of antiretroviral therapy on bone metabolism markers in HIV-seropositive patients.

OBJECTIVE: To evaluate the impact of antiretroviral therapy (ART) on bone and mineral metabolism and to determine the occurrence of osteopenia and/or osteoporosis in HIV-infected patients taking ART or not. METHODS: A cross-sectional study was conducted on 50 HIV-seropositive adult men treated with or not treated with ART. Dual energy X-ray absorptiometry (DXA) was performed and biochemical analyses of the following markers were carried out: FSH, LH, testosterone, total calcium, phosphorus (Pi), magnesium (Mg), albumin, 24h calcium, creatinine, urea, parathormone (PTH), insulin-like growth factor 1 (IGF-I), 25 hydroxyvitamin D (25-OH-D), osteocalcin, and urinary deoxypyridinoline (DPD). The participants were divided into two groups according to ART use or not: Group A, 10 treatment-naive subjects; Group B, ART use for >2years, subdivided into: Group B1, 10 subjects treated with protease inhibitors (PIs) and nucleoside/nucleotide analog reverse transcriptase inhibitors (NRTIs) and Group B2, 10 subjects treated with NRTIs and non-nucleoside analog reverse transcriptase inhibitors (NNRTIs); and Group C, subjects treated with ART <2years, subdivided into: Group C1, 10 subjects treated with PIs and NRTIs and Group C2, 10 subjects treated with NRTIs and NNRTIs. RESULTS: The values of the bone formation marker, osteocalcin, were normal in all groups, whereas urinary DPD values were increased in all groups. Whole body DXA revealed a higher percentage of osteopenia (80%) in Group B2. Lumbar spine DXA showed osteoporosis in Groups A and B1 (10%) and total femur DXA in Group B2 (10%). CONCLUSION: The increased bone reabsorption marker indicated a high reabsorptive activity of bone tissue. These data indicate a greater osteoclastic activity in bone loss in HIV-infected patients on ART.